Directional antenna system



Filed Oct. 19. 1948 IN V EN TOR.

E 2 at a E $7 a a a l J E Q m; 2 2 mm 2 @Jifi KLASS POSI'HUMUS BY lw AGHVI Patented May 13, l952 DIRECTIONAL ANTENNA SYSTEM Klaas Posthumus, Eindhoven, Netherlands, as-

signor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee ApplicationOctober 1 9, 1948, Serial No. 55,316 In the Netherlands December 23, 1947 The invention relates to improvements in or modifications of the invention described and claimed in the copending U. S. application of the same inventor filed on January 16, 1948 and given Serial Number 2,774. In said application is described inter alia a frame aerial in which for the purpose of increasing the radiation resistance provision is made of a number of short-circuit turns extending from the coil periphery in an outward direction and occupying together an annular surface surrounding the coil former.

These short-circuit turns are preferably constituted by sector-shaped metal plates, operating as such, which for the sake of simplicity, will be referred to hereinafter as concentrator segments.

Frame aerials according to the above-identified copending application have the advantage of being of very simple construction. Furthermore, if the circumferential length of the frame aerial exceeds the operation wavelength, the natural frequency of the frame aerial may be materially higher than the frequency corresponding to the operation wavelength and the frame aerial exhibits remarkable favourable properties for transmission or reception of wide frequency bands of horizontally polarised energy.

The present invention relates to a further improvement of the frame aerials described in the copending application and may be applied with particular advantage, for example, to radio course-making transmitters in which carrierwave energy and sideband energy are fed to different aerials for transmission with different directional diagrams. 5

According to the invention, in an aerial system comprising a number of frame aerialsconstructe'd in accordance with the description in the preamble to the copending application, the said aerials are located in one plane and adjacent frame aerials have at least one common shortcircuit turn. The spacing between the center of adjacent frame aerials may thus be smaller than the sum of the corresponding spacings between the frame aerial centre and outer periphery of the annular surface occupied by associated shortcircuit turns.

In known aerial systems for horizontal polarisation transmission with the use of various frame aerials, for example one central aerial and two aerials arranged one on each side thereof, use being made of aerials known as Alford-loops, it was impossible, in view of the small permissible spacing between the outer aerials, to arrange the central aerial in the plane of the two other aerials in between and, in order to avoid radiation'fof 7 Claims. (01. 250-5355) undue polarisation the central aerial had to be split up into two aerials which were arranged respectively above and below the plane of the outer aerials.

The present invention permits of the frame aerials being as it were intertwined" and dispenses with the splitting up of the central aerial.

In order that the invention may be more clearly understood and readily carried into effect, it will now be described more fully with reference to the accompanying drawing, in which Figs. 1 and 2 show, by way of example, two preferred embodiments of aerial systems according to the invention comprising respectively 3 and 5 frame aerials.

Fig. 1 shows an aerial system comprising three frame-aerial coils I, 2 and 3, which is particularlysuitable for use in beacon transmitters for guide plane indication by the amplitude-comparison method, the carrier-wave energy for unidirectional transmission being fed to the central frame-aerial coil 2 and energy modulated with the use of the outer frame aerials I and 3 5 by means of carrier-wave suppression and different signal frequencies (for example and c./s.) being transmitted with an eight-shaped directional diagram (beacon transmitter type SCS 51).

In order to increase the active frame surface area or else radiation resistance, each of the frame-aerial coils is surrounded by four concentrator segments co-operating therewith: coil I by segments 4 to 1, coil 2 by segments 1 to ID and coil 3 by segments ill to l3. These concentrator segments essentially transmit the current from a frame-aerial coil to the outer periphery of the associated segments.

Of these concentrator segments, the segments i and II] are in common to the frame-aerial coils i, 2 and 2, 3 respectively flanking these segments.

Since the aerials I and 3 with associated segments are arranged symmetrically to the central aerial, the outer aerials have no harmful effect on the central aerial. Otherwise, unduly tight couplings between the various frame-aerial coils with their associated concentrator segments are avoided by rendering the coupling between the two concentrator segments 1 and I0 which are in common to two frame-aerial coils and other concentrator segments less tight than the relative coupling between these other concentrator segments; this is achieved by suitable choice of the size of the gaps between the concentrator segments in the manner shown in Fig. 1. It should be noted that the coupling between any concentrator segments and the corresponding frameaerial coils is invariably made equally tight.

Fig. 2 shows an aerial system comprising 5 frame-aerial coils, four of which, to wit, [4, I5, l6 and H, are arranged at the corners of a square and the fifth frame-aerial coil [8 being arranged centrally to the others. This aerial system is particularly suitable for transmission of a directional field of horizontally polarised energy?" rotating in a low-frequency rhythm, the carrier.- Wave energy being fed to the central aerial'an'd the other aerials having fedto them the sideband: energy produced by using carrieri-wavesuppres sion to cause phase-shifted signals.-to:-modulate the frequency corresponding withthe desired rotation frequency.

The central frame-aerial coil is surrounded by four concentrator segments l9 to 22;.each of:

which is, moreover, associated with one of the other frame-aerial coils IE to I 1,. whichhave further concentrator segments 23 to 2 5g .26 to 2-8,-

29: to 3|. and 32 to 34. The coupling:g-apsibe-v tween adjacent concentrator segmentsarechosen in a-manner similar to thatof. Fig. Lin-accordance with the-desired coupling.

The concentrator segments surrounding aframe-aerial coil may be subdivided, in the manner described in the copending application, in a tangential and/or a radial direction, if'restriction of the natural frequency of the aerial sys-- tem requires it or renders it desirable with a viewto obtaining the mean operation frequency.

In the foregoing the connecting point of the supply leads. for the various-frame-aerial coils has not been discussed. In the two embodi mentsshown the supply conductorsare diagrammatically shown and arranged so asto ensure: minimum harmful effect on the shape of the-dcsired radiation diagrams.

It is obvious thatframe-aerial systems similar to the embodiments discussed may be, usedfor receiving. purposes, interalia for beacon receivers in which use'is made of aerial systems for reception by the amplitude-comparison method with radiation diagrams overlappingone another orelse for so-called rotary field-receivers.

What I claim is:

1. A directional antenna system comprising: plurality offrame antenna structures eachvconstitutjed by a centrally: disposed. open+circuited coil and a group of shortF-circuited loopsiinduc tively; coupled'to said coil and circumferentially arranged. thereabout, the loops extending-1. out-v wardly from the periphery of said coil andbein'g: shaped to. defineadjoining; segments. an an? nular surface surrounding said: coil, said frame: aerial structures being disposedat adjacent poi sitions in a single plane, adjacent structures having. at least one short-circuited'loop incommon.

2. An arrangement, as set forthinclaim 1, wherein the spacing between the center of the coil in one of saidstructures andthe center" of.- the' coil in the adj acent structure? is smaller. than the sum. of'the corresponding spacingszbetween the center of the coil and the =outerperipl'i'eryofi' the annular surface occupied by the short-en'- cuitedsloops in said one of said structures.

3. An arrangement, as set forth in claim 1,. wherein the. coupling of. short-circuited. loops common to two frame aerial structures; to others short-circuited loops is less than the coupling between these other. short-circuited loops'stosone another.

4; A. directional antenna system comprising: a

plurality of frame aerial structures each constituted by a centrally disposed open-circuited single turn coil, and a plurality of short-circuited loops formed by metallic plates inductively coupled to said coil and circumferentially arranged thereabout, the plates extending outwardly from: the periphery of said coil and being shaped to" defineadjoining segments in an annular surface surrounding said coil, said frame aerial structures being disposed at adjacent positions in a single plane, adjacent structures having-at least oneplate incommon.

5. A, directional. antenna system comprising three frame? aerial. structures each constituted by' acentrallytdisposed open-circuited single turn coil and four metallic plates inductively coupled tosaidlcoilandicircumferentially arranged thereabout, said plates extending outwardly from the periphery of said coil and being shaped to define adjoining segments inan annular surface surrounding saidcoil, saidframe aerial structures beingadisposed at adjacentpositions in a single plane; adjacent.- structureshaving one plate in common;

Grl'n. alra'dio beaconfor directional plane indicatiomby' the amplitude comparison method whereimcarrier wave: energy and side-band energy: are transrnitted. by separateaerials, a directional antenna system comprising three frame aerial structures each constituted by a centrally disposed:openeci-rcuited'coil and a plurality of short-circuited loops inductively coupled to said coil and= circumferentially arranged thereabout, the wloopsex-tending outwardly from the periphery of: said coil andabeingshaped to define adjoining segments inanannular surface surrounding said coil, one-ofsaid-frame aerial structures being disposedat agiven: position'in a single plane, said carrier; wave energy being supplied to the coil insaid-one' of said structures, the remaining two ofisaid; structures-being arranged at either side ofsaid onefof. said-structures in saidsingle plane, the-aside-band energy b'eingsupplie'd to the coils in; said remainingzstructures; .each of'th'e remaining: structures-havinga short-circuited loop in common with said one of. said: structures.

7. A directional: antenna system comprising five frame-aerial structures. eachconstituted by a} centrally disposed open-.circuited coil and four short-circuitedloops inductively coupled to said coil and circumferentially' arranged thereabout, theiloopsrextending"outwardly from the periphery ofisai'di coil and. beingshaped. to define adjoining segments in an annular surface surrounding said coil; said. structures being adjacently disposed within. a; single" plane'; the. coils in four of said structures being: disposed; at the respective corn'ers off'a square,.th'et coil in the fifth structure being disposed at: the center'of said square, each loop-in saidsfif-th structure being in common with one -l'oop in eaclr-ofthefour of said structures.

' KLAAS" POSTHUMUS.

REFERENCES CITED The following references are. of record in file of this patent? UNITED STATES PATENTS the 

